Ninety percent of asians, 75% of african-americans, and a much smaller percent of northern europeans are lactose intolerant. why do you suppose we see this pattern?

This pattern probably exists because of an evolutionary process.

Explanation:

Originally, the consumption of milk and dairy products was more common in northern Europe than in Asia and Africa, this allowed the northern European ancestors to evolve and make their organisms lactose tolerant. This evolution passed on to their descendants and allowed lactose tolerance to be more frequent in this region of the world. On the other hand, dairy consumption was not common in Asia and Africa, so this evolutionary process did not occur with the inhabitants of this region.

Lactose intolerance is a digestive disorder associated with low or no lactase production by the small intestine. Symptoms vary depending on whether or not milk and dairy products are ingested.

exposure to hazardous carcinogens and toxic substances can cause breathing problems, such as copd and various types of cancer. it also increases the risk of heart attacks and strokes and has serious (but no less unattractive) side effects, such as aging, yellow teeth, a terrible smell and damage to the vocal cords.